Electrical system and appliance



Feb. 2, 1932. s. E. LEONARD. JR

ELECTRICAL SYSTEM AND lAPPLIANGE 3 Sheets-Sheet l Mlm Filed Oct. 8, 1928 DUT PUT UUTPUT INPUT P U K m F ATTORNEY m/ou/lam,

Feb. 2, 1932. s. E. LEONARD. JR

ELECTRICAL SYSTEM AND APPLIANCE 3 Sheets-Sheet 2 Filed 001;. 8, 1928 T .0, n C E 9mm llllb.:

ATTORNEY Feb. 2, 1932v s. E. LEQNARD, JR 1,843,283

ELECTRICAL SYSTEM AND APPLIANCE Filedv Oct. 8, 1928 3 Sheets-Sheet 3 29 q .a1 3e M, WW l Mozgmm Patented Feb. 2, 1932 PAT FFICE SAMUEL E. LEONARD, JR., OF EAST CLEVELAND, OHIO ELECTRICAL SYSTEIlrI AND APPLIANGE Application led October 8, 1928. Serial No. 310,972.

My invention relates to electrical systems and appliances, and more particularly to a new and novel means for automatically exercising a restraining or directing influence over an electrical system or apparatus. The means involved includes an electric circuit for picking up or receiving electric energy, a device for converting that energy into light, and a second electric circuit containing means adapted to be iniiuenced by the light to control the output energy thereof, which may be used in various ways to exercise a restraining or directing influence over other electrical systems or apparatus. For example, the invention may be employed to control and stabilize the volume or power output of either a transmitting or receiving system, using alternating currents of low or high power, alternating currents of low or high frequency, a pulsating direct current, or any other electric current which may be used with the idea of means hereinafter shown and described. Stated more specifically, the invention may be utilized to automatically control and regur late the volume or power output of a radio broadcasting circuit, a repeater amplifier long-distance telephone circuit, a public address system or circuit, radio receiving circuits, television and picture circuits, high power transmission lines or circuits,. and systems or circuits using pulsating direct currents of high voltage ;-The purpose being to stabilize the output and prevent distortion should disturbance of the working balance, or overloading, of the main system occur.

As an exemplification of several uses to which the invention may be put reference concept applied to radio broadcasting and long-distance telephone circuits, respectively. Fig. 4 is a diagram corresponding to Fig. 1, but in this case a single grid power tube is used in the first or preliminary stage of amplification in the output circult. Fig. 5

is a schematic diagram of a long-distance telephone circuit containing a repeater amplilier, including a volume control circuit in transformer coupling connection therewith. Fig. 6 is a diagram showing the invention applied to a radio receiving circuit. Fig. 7 is a diagram showing the control circuit applied to a radio transmitting circuit in the radio frequency amplifier stage.

Now, referring to Fig. 1, the main circuit A therein represents an audio frequency circuit, for example, a broadcasting circuit which includes a microphone 2, a microphone battery 8, an input transformer 4, the first power tube 5 or preliminary amplifier handling very small volumes, a modulator transformer 6, a modulator tube 7, a constant current coil 8, an oscillator tube 9, an oscillatory circuit 10, and an antenna counterpoise or output circuit 1l. Thus it will be seen that circuit A is in the main, of a conventional type, excepting that power tube 5 in this case embodies four electrodes, or two grids l2 and 14. respectively. One of these grids, grid 14 for example, is connected in a second circuit B, which may be termed a volume control circuit, inasmuch as it is used to cut down or reduce amplification during abnormal operating conditions. Under normal broadcasting conditions grid 14 does not influence the normal operation of tube 5, but when an objectionable high volume is picked up the power change is greatly amplified and objectional distortion takes place in the output, it being known that the greater the amplification in a broadcasting system, the greater the radio-frequency is modulated, and therefore the greater the power change or the radiated field of the radio-frequency circuit. Correction and relief, heretofore, has been dependent upon manual control and regulation of the output. In the present system volume control circuit B is designed to eliminate the human element of control, and create steady and uniform volume of output automatically under abnormal conditions of input. Thus, control circuit B includes a pick-up device, which may be a suitable antenna or a high frequency coil or rotatable loop 15 inductively coupled to the high-frequency transmitter circuit A. This coil or loop 15 is connected to a special neon tube 16 or any other equivalent light emitting device enclosed within a light-proof container 17 together with a photo-electric cell 18. An increase in power beyond given values of the radio-frequency output will cause the neon tube 1G to glow, and the light rays in striking the plate or electron emitter of the photo-electric cell 18 cause a change in the resistance of the cell, thereby permitting` electric current to flow in control circuit B. The output energy of the photo-cell is very small, and therefore means for amplifying the power many thousand times is included in control circuit B. To exemplify, a vacuum tube amplifier 19 may be usen, and a suitable resistance or impedance 20 to match the plate to filament impedance of the tube is connected to the plate circuit 21 thereof, with two leads 22 and 23, extending therefrom to the extra grid 14 and filament 24, respectively, of the first tube 5 in power transmitting circuit A. lVhen the neon tube glows and current flows in control circuit B a negative potential is put on grid 14 in tube 5. Accordingly, when tube 5 is influenced by control circuit B it functions momentarily as a pressure reducing valve, although primarily a power amplifier.

The neon tube and photo-electric cell are coupled to the radio-frequency portion of the transmitter in such a way that with an unmodulated signal the neon tube is practically free from ionization or light. However, as the circuit is modulated and an increase in radio-frequency power effected the neon tube will glow between the near portions of the electrodes, and as the radio-frequency power increases a greater portion of the electrodes are ionized and more light created. The neon tube is set very close to the sensitive photocell, and the cell changes its flow of current in proportion to the amount of light emitted from tube 16. The current actuates vacuum tube amplifier 19 and the output is fed into the auxiliary grid 14 of the input amplifier' tube 5 in power transmitting circuit A. This causes a voltage drop over plate resistor or impedance 20, and a negative potential is immediately placed on the extra grid 14 of preliminary amplifier tube 5, an action which makes the preliminary amplifier less sensitive and cuts down the output amplification of the first tube and all successive stages of amplification until the radio frequency amplitude diminishes sufficiently to extinguish or stop the glow of the neon tube, thus restoring transmitter Circuit A to a normal operating condition. Tn that connection it should be understood that the action is instantaneous and automatic, and that the effect is to provide a good steady volume to the receiver.

Control circuit B may be coupled to any one of the amplifier stages of transmission circuit A, but it is preferably connected to the first stage, or one of the lower power stages, for better quality and more sensitive control. The output of the transmission system may be by an antenna and counterpoise as shown in Fig. 1, or to antenna and ground as delineated in Fig. 2. Different pick-up devices may be used for control circuit B, either a coil or loop as represented in Figs. 1 and 4, an antenna and ground as shown in Fig. 2, or a conductive coupling as illustrated in Figs. 3 and 5. Fig. 5 also represents a portion of a long-distance telephone circuit A containing one or more stages of amplification such as used in carrier telephones or repeater amplifier long-distance telephone circuits and in picture transmission circuits.

In coupling the control device to the output side of either a telephone circuit, or to a broadcasting radio-frequency circuit, connection would be had with the input amplifier, and the control device used as described to cut down amplification should the input produce objectionable volume. Preferably, control is effected through or by a double grid amplifier tube or by creating additional negative grid bias on a conventional power tube.

To illustrate the use of the invention with a conventional power tube instead of a double grid tube T show in Fig. 4 a transmitting circuit A which is substantially the same as in Fig. 1, excepting that the first power tube 5 is of the conventional three element` type, that is, it includes only a single grid 12 instead of two grids, and instead of the grid bias of the tube being obtained from a C or bias battery 25 alone as shown in Fig. 1, the grid is connected in series with the plate resistor of the photo-electric cell amplifier' 19, see Fig. 4. This arrangement functions as follows: lVhen a signal originates at microphone 2 it is transferred to grid 12 of amplifier tube 5. The potential of the grid of this tube under normal conditions is determined by the voltage of the bias battery or the C battery 25 shown in Fig. 4. The signal is then transferred to the modulator tube 7 by the coupling transformer 6. The modulator tube in turn modulates the oscillator tube 9 which radiates the energy to the antenna 11, the power radiated depending on the amount of modulation applied by the modulator tube.

The pickup device 15 is so coupled that on high peaks of modulation the neon or light emitting tube 16 will glow. As this tube is in a light proof container 17 with the sensitive photo-electric cell 18 the light waves are turned into feeble pulses of electrical energy of positive charge which is applied to the grid of amplifier tube 19 which is so adjusted to be normally quite negative thereby holding` the plate current of the tube to a minimum. The grid 12 of the first power tube 5 derives its negative bias by the normal bias battery or C battery 25 together with the additional voltage obtained from the voltage drop across the resistor or impedance. The first amplifier tube 5 Will be Working under normal condition as long as the plate current is held to a minimum in the photo-electric cell amplifier tube 19.

As the grid of the amplifier 19 is made positive or less negative, as a result of the glowing of the neon tube caused by too high modulation, current begins to flow in the plate resistor or impedance and a greater voltage drop is produced across this resistor or impedance which adds additional negative grid bias to the first amplifier tube 5. The additional grid bias causes the tube 5 to cut down its output power which in turn cuts the amount of signal to modulator tube 7, there` by decreasing the amount of modulation and cutting down the output of the radio-frequency oscillator, thus restoring neon tube 16 to the normal condition of no ionization or darkness, which in turn restores the entire circuit to a normal condition. The volume, therefore, is controlled automatically by the variation of the negative grid bias of the first amplifier tube 5 which is Working under normal conditions until an overload occurs, at which time its output is cut down because of the additional negative grid bias applied as a result of the voltage drop over the plate resistor or impedance. The voltage drop is produced by the increase in plate current caused by the grid of this tube becoming less negative, Which is caused by the positive energy Vgiven off by photo-electric cell 18 when energized by light Waves from neon lamp or light emitter 16 as a result of peak or high modulation of the radio frequency oscillator or radiating circuit 10.

In Fig. 5 l show the control device B coupled to a conventional telephone repeater circuit A2, by means of a transformer 15, the arrangement operatingin 4substantially the same Way and for the same purpose as the circuit shown in Fig. et. The connections for control circuit B are the same in all other respects as shown in Fig. 4. The invention may also be employed in radio receiving circuits, and other apparatus as Well. rllhus the control device may be utilized to control radio-frequency circuits from audio frequencies, audio frequencies from radio frequencies, audio frequencies from audio fre! d quencies, and radio frequencies from radio frequencies, as the quality of transmission is not disturbed because of change 1n frequency characteristics. The control 1s effected by producing light changes, say darkness t0 light, or a variation of amount of light, and While such changes may be utilized to reduce volume or output of an electrical system, it is also feasible to employ the same control device to increase volume by maintaining a condition of ionization or light at all times and then reducing it to darkness under abnormal conditions.

In Fig. 6 l show a diagram of a volume control circuit B coupled to a radio receiving circuit A3 of a conventional type which includes an antenna 26, a radio-frequency amplifying tube 27, a radio-frequency transformer 28, a detector tube 29, a grid leak and condenser 30, a first audio amplier tube 31, a second audio amplifier tube 32, and a loud speaker or other output device 33. Control circuit B in this case includes a neon lamp 16 in a pick-up circuit o, a photo-electric cell 18, and an amplifier tube 19 With a plate resistor or impedance 2O connected With the grid 12 of one of the amplifier tubes in receiving circuit A3, preferably the first audio amplifier tube 27. The pick-up circuit I) includes a transformer 34 connected in series With the output circuit 35 which operates the loud speaker 33 or other device or instrument used for reproducing, recording or transmitting the signals amplified to audio frequency. A direct current potential is also maintained in pickup circuit to cause the neon tube to be ionized or illuminated to a given extent at all times.

rl'he action of the circuit in this case is as follows: The D. C. potential in pickup circuit Z) is adjusted so that the action of control circuit B places the normal grid bias on grid 12 of the radio frequency amplifier tube 27. As varying volume is received through coupling transformer 34;, more or less energy is added to the D. C. energy already induced in the pickup circuit. rfhe result is a variation of light emitted from neon tube 1G on either side of an already established condition of ionization. These variations in light energize the photo-electric cell and its amplifier, and the resulting varying D. C. potential obtained by the voltage drop across the plate resistor 20 of the photo-electric cell amplifier tube 19, is applied to the radio frequency amplifier' tube 27, thereby controlling volume by the use of the most appropriate grid bias for the particular receiving condition. T his arrangement allows for an increase in sensitivity of the tube 27 as Well as a decrease, and as pickup circuit is also normally charged With D. C. potential to produce steady ionization of neon tube, the alternating current superimposed from output of the receiver circuit through coupling transformer 34 causes the ionization to vary up and down, according to amounts and characteristics of the A. C. applied.

In controlling a radioreceiving circuit With or Without using a D. C. potential in pickup circuit Z9, the main circuit A3 may be set or adjusted to receive the maximum signals, and the volume control circuit B set or so adjusted that the neon tube Will glow on high peaks of modulation or undesirable volunie, thereby limiting the power output of the first radio frequency stage and leveling the peak loads or abnormal volume of output. Thus, in either a transmitting or receiving system the invention operates to control and level abnormal output peaks of volume, signals, or passages of speech or music, it being further understood that the incoming volume is set or adj usted to point Where low volume or low passages of music or speech provide sufficient volume through the transmitters or amplifiers for normal operations.

In Fig. 7, the control circuit B is shown as coupled to a radio transmitting circuit A4 Which is fundamentally of the modulated master oscillator type except that the radio frequency power amplifier stage is volume controlled by the use of a two grid tube 37 corresponding to tube 5 in Fig. 1. T he action is as follows: Assuming a signal originates, such as a telephone, broadcast, telegraph or television signal, it is coupled through coupling transformer 38 to a modulator tube 89 which modulates a master oscillator tube 40 in the conventional constant current system of modulation. The signal. is then amplified by the next succeeding radio frequency amplifier tube 37 of the special double grid type, and again transferred by the medium of a radio frequency transformer 41 to the last stage radio frequency amplifier tube 42 and thence through the coupling circuit 43 to the radiating circuit or antenna 44 and ground.

Volume control circuit B is so adjusted that the neon tube 1G will be caused to glovvv on an overload or signals over a predetermined strength or volume, thereby energizing photo-electric cell 1S Which in turn causes the photo-electric cell amplifier tube 19 to draw plate current, thereby creating a negative bias on one of the grids in the double grid radio frequency amplifier tube 37, and in that Way cutting doivn its output and causing the main circuit to reduce itself to normal operating conditions. By adjustment of control circuit B, l mean, by adjusting the coupling between the tivo circuits, by adjustment on the photo-electric amplifier tube plate impedance, by a grid bias adjustment to photoelectric amplifier tube, or by reversing the grid connections to the grids of the tube being regulated from the volume control device. And While 1 speak of the invention as a volume control device in general it is not limited to reducing the volume only.

Thus, referring to the control device itself, it may be used for many other purposes than as already described. For example, it may be used independently of broadcast, telephone or television apparatus, to pick up energy at predetermined frequencies and cha-nge this energy to direct current in unusual exactness and fineness in accordance With the volume of A. C. received. As a result of this action either radio frequencies or audio frequencies may be used to actuate this type of volume control device to do many special types of work Where varying l). C. potential is required. To foster that purpose the sensitive photo-electric cell 18 is placed in a. light proof container 17 in conjunction With the neon tube 16 which is adapted to be energized, say for example, by a tuned radio frequency circuit or a coupled audio frequency circuit. Under conditions that are abnormal the neon tube is caused to ionize or gloiv, giving off light Waves, assuming sufiicient voltage is produced across the terminals of tube 1G When picked up from the tuned circuit in the case of radio frequency and from a step-up transformer in case of audio frequencies. The light rays with the help of a reflector 45 concentrate their energy to the sensitive photo-electric cell 1S which is charged with comparatively high positive voltage from the B battery shown in the diagram. No other light Waves are allowed to effect the photo-electric cell as the light proof container excludes all outside light. As a result a high positive potential is applied to one tern'iinal of cell 18, and the other terminal which is the electron emitter, connected to the grid of the photo-electric amplifier tube 19. Due to the high resistance of t ie photo-electric cell the positive potential on the one electrode does not have any material effect normally on the other electrode or emitter of the cell, thereby not affecting the potential to the grid of amplifier tube 19 as the grid of this tube is very carefully biased to such a` negative point so that very little or practically no plate current flows in the tube. Accordingly, the photoelectric cell has one electrode charged highly positive, and as light strikes the other elec trede, connected to the grid of the photoelectric cell amplifier tube, electron emission occurs thereby breaking down the high resistance of the cell and placing a. positive charge to the already negatively charged grid of amplifier tube 19. This circuit for tube 19 includes A, B, and C batteries used in a conventional manner. ln series with the B or plate battery, however, is a plate resistance or plate impedance 2O equal approximately to the tube impedance. The grid bias battery is so adjusted With a voltage divider as to give very fine regulation of the grid potential and is also so adjusted as to cut the plate current to a minimum by the application of a. negative potential to the `grid. ller-Jever, the adjustment is kept to such a point that a slight change of the grid potential to a point less negative will cause the tube to draw plate current, and a very high resistance is placed in series with the grid and the bias battery so that the grid may be energized by the photo-electric cell Without interruption. ln action the photoelectric cell places a positive potential to the grid of the amplifier tube 19, causing it to become less negative or possibly even positive in respect to its filament, thereby causing maximum plate current to flow in varying degrees of current from minimum to maximum according to potential applied to the grid, or according` to the amount of light striking the electron emitter of the photoelectric cell.

Having produced a varying plate current in the amplifying tube 19, the result of two leads Q2 and 23 taken from across the plate resistor or impedance is as follows: Under non-signaling conditions when the grid is negative, the plate current of a tube 19, is a minimum, and therefore the voltage drop across the resistor or impedance is a minimum. However, Linder heavy signalling conditions when the grid is positive, maximum plate current will flow in tube 19 and cause the `greatest voltage drop in the plate resistor or impedance. Any point between these two conditions are very carefully and delicately reproduced in voltage drop across the resistor or impedance. Voltage is obtained from the plate resistor or impedance due to the well known law that a difference in potential will occur across an impedance when current flows through the resistance or impedance. The polarity of this potential is obvious the point at the positive battery connection, being positive in respect to the plate end or the voltage drop end, which is negative. The potential across this resistor or impedance, is therefore in accordance, or will vary according to the volume or the amount of input which causes ionization of the neon tube. The control device is therefore particularly adaptable to circuits using vacuum tubes. However, as varying D. C. potentials are obtained the device can be used in other electric circuits, 0r in any vacuum tube circuit, to actuate many different devices.

Preferably, the neon tube or light emitter includes a special arrangement of electrodes, the two electrodes 46 and 47 being spaced closely apart at their extremities and then spreading or diverging at an acute angle, so that variable ionization effects will be produced as the voltage changes. Thus the voltage of the pickup may be only sufficient to span the closest gap between the electrodes, and as the voltages to the tube is increased the ionization shifts or spreads along the electrodes where spread wider apart thus transmitting a greater amount of light to the photo-electric cell and causing a greater variation in actions and results.

What I claim is:

1. In a radiant energy system, a main circuit containing electric-current input and amplifying devices, including a power limiting valve, in combination with a control circuit coupled to said valve in said main circuit and including electric-current pick-up and amplifying devices, and means for tuning the coupling of said circuits to hold said valve inactive with respect to its power limiting action within a predetermined normal range of input in said main circuit and to actuate said valve to cut down the output of said main circuit under abnormal input.

2. In a radiant energy system, a main circuit containing electric-current input and output devices, including an electric volumelimiting valve, in combination with a current feed-back circuit for said valve, including a light emitter, a photo-electric cell, and an electric-current amplifier.

8. In a radio frequency transmitting system, a main circuit, including energy input and output apparatus, in combination with a second circuit having means for picking up a part 0f the radiant output energy of the main circuit, including means for converting the energy picked up into light and also means for utilizing the light to limit the volume of the output of said main system.

4. In a radio frequency transmitting system, a main circuit containing electrical input and output appliances, a separate circuit coupled to the output side of the main circuit and containing a light emitting device, and a third circuit containing power amplifying means, a power tube and means capable of being influenced by said lighting device for producing a limiting effect on the plate current in said tube.

5. In a radio frequency transmitting system, a main electric circuit containing a power tube and output devices, a second circuit coupled to the output side of said main circuit and containing an electric lamp, and a third circuit coupled to said power tube containing means for controlling the operation of said tube, said means being capable of being influenced by the light rays emitted from said lamp.

6. In a radio frequency transmitting system, ay main electric circuit containing an output device, a circuit containing a light tube coupled to the output device of said main circuit, a second circuit containing an electrical resistance sensitive to the emission of light from said tube, means for excluding all other extraneous light from said tube, a separate source of electric current for said second circuit, and a controlling device for the electric current flowing in said main circuit connected to said second circuit and subject to the electric current owing therethrough.

7. In a radio frequency transmitting system, according to claim 6, a light tube consisting of a neon lamp, a photo-electric cell, as electrical resistance in said second circuit, and means to regulate the flow of current through said second circuit.

8. In a radio frequency transmitting system, a main circuit including input and output devices, a circuit containing a light tube coupled to the output side of said main eircuit, a high resistance device subject to the influence of light emit-ted from said light tube, a power amplifying circuit containing 5 a resistor coupled to said high resistance device, and means subject to the influence of the output current of the amplifying circuit to limit the output of said main circuit.

9. In a radio frequency transmitting sysl tem, a main circuit containing input and output devices and including a vacuum tube having a pair of grids, and a control circuit coupled to the output side of said main circuit, including means for producing a voltage l drop and a change in potential on one of said grids with limiting elfect on the output of the main circuit.

10. In a radio transmitting system, a main circuit, including a power limiting valve in o combination with a control circuit, power pick-up means coupling said control circuit with the output side of said main circuit when the output energy rises above a certain value, and means for tuning said circuits and means for varying the coupling between the output side of said main circuit and said controlling circuit, to automatically limit the output of the power circuit during overloading of the system.

a 1l. In a radio transmitting system, a main circuit containing electric current input and amplifying devices, including a. power limiting valve in combination with a control circuit inductively and variably coupled in a non-metallic circuit with the output side of the main circuit, and means for tuning said circuits to prevent power limiting action of said valve within the normal range of input of the system and permitting pow- Q er limiting action of said valve and level and limit the output under abnormal input.

12. In a radio broadcasting transmitter, a

main circuit containing electric current in put and output devices, including a-volume 5 control valve in combination with a current feed back circuit for said valve, including a lighting emitter, a photo-electric cell and an electric current amplifier. h

In testimony whereof I aihx my signature;

SAMUEL E. LEONARD, JR. 

